Some touch panel display devices include a touch panel that detects input coordinates based on changes in resistance by the pressing operation, and one of such touch panel display devices is disclosed in, for example, Patent Document 1.
A screen input type display device disclosed in Patent Document 1 is configured such that a first base substrate formed of a polyethylene terephthalate film and a second base substrate made of glass are arranged to face each other. The first base substrate has, on a surface thereof facing the second base substrate, a first resistance film made of ITO and a first wiring electrode electrically connected to the first resistance film. The second base substrate has, on a surface thereof facing the first base substrate, a second resistance film made of ITO, a second wiring electrode electrically connected to the second resistance film, and an inter-substrate connection wiring electrode electrically connected to the first resistance film. The first wiring electrode and the inter-substrate connection wiring electrode are electrically connected through a conductive adhesive member. The conductive adhesive member includes a pressure-sensitive adhesive material and conductive particles dispersed in the pressure-sensitive adhesive material. Further, each of the second wiring electrode and the inter-substrate connection wiring electrode is formed by applying a conductive paste such as a silver paste by printing.
In the screen input type display device of Patent Document 1, the inter-substrate connection wiring electrode, which uses a silver paste (obtained by dispersing silver particles in a resin), has a relatively larger resistance than metal wiring made of, for example, aluminum. Thus, in the screen input type display device of Patent Document 1, the large thickness of the silver paste is required in order to reduce variations in applied voltage which are caused by the relatively large resistance. It is therefore difficult to make the screen input type display device of Patent Document 1 sufficiently thin.
In the screen input type display device of Patent Document 1, furthermore, even if metal wiring of aluminum having a relatively low resistance is used instead of a silver paste, an oxide film is formed on the surface of the metal wiring, which may cause unstable electrical connection between the metal wiring (inter-substrate connection wiring electrode) and the first wiring electrode.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2002-41231